Over the past 40 years, it has been found that the application of weak non-thermal electromagnetic fields (“EMF”) can result in physiologically meaningful in vivo and in vitro bioeffects. Time-varying electromagnetic fields, comprising EMF, ranging from several Hertz to about 100 GHz, have been found to be clinically beneficial when used as a therapy for reducing pain levels for patients undergoing surgical procedures, promoting healing in patients with chronic wounds or bone fractures, and reducing inflammation or edema in injuries (e.g. sprains).
Presently several EMF devices constitute the standard armamentarium of orthopaedic clinical practice for treatment of difficult to heal fractures. The success rate for these devices has been very high. The database for this indication is large enough to enable its recommended use as a safe, non-surgical, non-invasive alternative to a first bone graft. Additional clinical indications for these technologies have been reported in double blind studies for treatment of avascular necrosis, tendinitis, osteoarthritis, wound repair, blood circulation and pain from arthritis as well as other musculoskeletal injuries.
In addition, cellular studies have addressed effects of weak electromagnetic fields on both signal transduction pathways and growth factor synthesis. It has been shown that EMF stimulates secretion of growth factors after a short, trigger-like duration. Ion/ligand binding processes at intracellular buffers attached to the cell membrane are an initial EMF target pathway structure. The clinical relevance to treatments, for example, of bone repair, is up-regulation such as modulation, of growth factor production as part of normal molecular regulation of bone repair. Cellular level studies have shown effects on calcium ion transport, cell proliferation, Insulin Growth Factor (“IGF-II”) release, and IGF-II receptor expression in osteoblasts. Effects on Insulin Growth Factor-I (“IGF-I”) and IGF-II have also been demonstrated in rat fracture callus. Pulsed electromagnetic fields (“PEMF”) have also been shown to have an effect on transforming growth factor beta (“TGF-β”) messenger RNA (“mRNA”) in a bone induction model in a rat. Studies have also demonstrated up-regulation of TGF-β mRNA by PEMF in human osteoblast-like cell line designated MG-63, wherein there were increases in TGF-β1, collagen, and osteocalcin synthesis. PEMF stimulated an increase in TGF-β1 in both hypertrophic and atrophic cells from human non-union tissue.
Further studies demonstrated an increase in both TGF-β1 mRNA and protein in osteoblast cultures resulting from a direct effect of EMF on a calcium/calmodulin-dependent pathway. Cartilage cell studies have shown similar increases in TGF-β1 mRNA and protein synthesis from EMF, demonstrating a therapeutic application to joint repair. U.S. Pat. No. 4,315,503 (1982) to Ryaby, U.S. Pat. No. 7,468,264 (2008) to Brighton and U.S. Pat. Nos. 5,723,001 (1998) and 7,744,524 (2010) to Pilla typify the research conducted in this field.
Despite the promising developments in EMF treatment, EMF therapies have been largely limited to treating patients without metal-containing implants or prosthetics. This is primarily because the much higher conductivity of metals, compared to tissue and body fluids, can reduce the desired EMF dosage for patient treatment, and/or alter the distribution, uniformity or pattern of the applied EMF. For example, the metal in joint implants may preferentially absorb or otherwise alter the shape of an applied electromagnetic field, which reduces the strength and range of the field. As such, beneficial EMF treatments have not been provided to the majority of patients undergoing procedures (such as knee or shoulder replacement) where metal-containing implants or prosthetics are used.
Accordingly, some embodiments described herein address the need for electromagnetic therapy devices (e.g., PEMF devices) that are compatible with metal implants, and provide methods for calibrating EMF delivery devices (e.g., “detuning”) such that the EMF devices can provide appropriate EMF treatment to a patient with a metal-containing implant or prosthesis. Additionally, other embodiments described provide EMF delivery devices and treatments to help promote healing and recovery by delivering EMF treatment to a target location in proximity to a metal-containing implant or prosthetic. Furthermore, because patients recovering from surgery often have reduced mobility, other embodiments described provide for easy-to-wear and adjustable EMF delivery devices. The described embodiments can be adjusted to be worn or placed near a target treatment location such as an operation site while accommodating the patient's need for flexibility and comfort.
Another challenge in maintaining the integrity of the electromagnetic field delivered for treatment arises from the EMF device itself. In some cases, the EMF device's own components can lack the requisite durability and resilience to maintain the shape and strength of the needed EMF. For example, EMF delivery devices often employ ductile metal coils or metal wires to deliver an electromagnetic field. Although such materials are advantageous for delivering electromagnetic fields, these materials also have the tendency to break from stress fatigue than can result from repeated bending and flexing, which may naturally occur from use. Moreover, once a coil or wire has been deformed or broken, its delivered EMF may no longer have the strength, shape, or structure appropriate for treatment. Therefore, some embodiments described herein provide for EMF devices having support members to maintain the integrity (e.g. structure, shape, resilience, or strength) of a generated EMF.